Following https://docs.substrate.io/tutorials/v3/ink-workshop/pt1/ , I run substrate-contracts-node --dev to start the node, but the Contract UI at https://contracts-ui.substrate.io/ shows Connection Error and cannot connect to Local Node, preventing contract deployment.

Any configuration to be changed ?

Running on Chrome, Apple M1 chip.

enter image description here

EDIT: it looks like a websocket connection error:

2022-04-22 14:50:15 Blocked connection to WebSockets server from untrusted origin: Some("https://paritytech.github.io")    

how can we allow the connection?

EDIT2: I've added --unsafe-ws-external to substrate-contracts-node command and Contract UI connects to LocalNode, but not sure this is the correct solution. (https://github.com/openethereum/parity-ethereum/issues/9678)

  • Can you add which browser you are using? Apr 22, 2022 at 6:49
  • @AlexanderTheißen running on Chrome , Apple M1 chip. Chrome error: WebSocket connection to 'ws://' failed: connect @ polkadot.25fc112e.js:23
    – mastro
    Apr 22, 2022 at 6:56

1 Answer 1


this error happens when the local node is not ran in development mode - need to run substrate-contracts-node --dev (https://github.com/paritytech/substrate-contracts-node/issues/50)

the problem was that I was running the executable from https://github.com/paritytech/substrate-contracts-node/releases, that starts the node in Local Testnet (instead of dev)

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